Dark kangaroo mouse (Microdipodops megacephalus)

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Dark kangaroo mouse fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Dark kangaroo mouse description

Named for its dark-furred back and long hind limbs and feet ⁽⁴⁾, the dark kangaroo mouse (Microdipodops megacephalus) is a bipedal rodent that generally moves around by hopping along on its strong hind legs, much like a kangaroo ^{(2) (5) (6) (7)}.

As the dark kangaroo mouse bounds across its sandy habitat on its large, fur-soled hind feet ^{(2) (3) (5)}, it uses its long tail for balance ⁽⁵⁾. On occasion, the dark kangaroo mouse also makes use of its short forelimbs for movement, scuttling around on four legs like other mouse species ⁽²⁾.

The dark kangaroo mouse has a proportionally large head ^{(2) (5)}, which is roughly the same size as its body ⁽⁸⁾. Its ears are large ^{(4) (5)}, and it has prominent eyes, a long snout and bushy whiskers ⁽⁴⁾. This species also has fur-lined external cheek pouches, which it uses to store and carry food ^{(2) (3) (5)}.

The long coat of the dark kangaroo mouse is soft and silky ⁽⁵⁾, with the upperparts being brownish, blackish or grey ^{(2) (3) (4) (5) (6)}. In contrast, the underparts are much paler, with a greyish or whitish hue ^{(3) (5) (6) (8)}. Conspicuous white spots of fur can be seen behind each ear ⁽³⁾, as well as at the base of the ear, the base of the whiskers, and above the eyes ⁽⁸⁾.

The tail of the dark kangaroo mouse is rather unusual in that it is thickest in the middle section, tapering both at the base and the tip ^{(2) (3) (6) (8) (9)}. The upper side of the tail is darker than the underside ⁽⁷⁾, and ends in a black tip ^{(5) (7)}.

There are currently 13 known subspecies of the dark kangaroo mouse, 2 of which are considered to be under threat ⁽¹⁰⁾.

Also known as

Owyhee River kangaroo mouse.

Size

Total length: 14 - 17.7 cm ⁽²⁾

Tail length: 7.6 - 10.3 cm ⁽³⁾

Hind foot length: 2.3 - 2.7 cm ⁽³⁾

Weight

10 - 17 g ⁽²⁾

Dark kangaroo mouse biology

The dark kangaroo mouse is strictly nocturnal ^{(1) (3) (5)}, only venturing out during the cooler desert nights when relative humidity is at its highest ⁽³⁾. This jumping rodent species is most active within the first two hours after sunset ^{(1) (8) (9)}, when it will forage for food out in open areas away from dense vegetation cover ^{(5) (8)}.

The diet of the dark kangaroo mouse consists mainly of small seeds ^{(1) (3) (5) (6) (8) (9)}, which it carries in its external cheek pouches back to its underground burrow system ^{(4) (5)}, where it stores the food in a cache ^{(1) (4)}. The dark kangaroo mouse also eats small insects ^{(1) (5) (6) (8) (9)}, such as beetles and butterfly larvae ⁽⁹⁾, particularly in the summer months ⁽⁴⁾. In addition, the dark kangaroo mouse has been reported to occasionally consume green vegetation ^{(3) (9)}.

The dark kangaroo mouse does not appear to actively drink water ^{(1) (5)}. Instead, it relies upon the water in its food ^{(5) (6)}, and reduces water loss by producing concentrated urine and dry faeces ⁽⁵⁾.

Interestingly, the dark kangaroo mouse also stores food as body fat within the bulge in the centre of its tail ^{(4) (5) (7)}, which enlarges during the summer as fat is deposited, and then diminishes in size during hibernation as it is used as a source of energy ^{(5) (7)}. This is a unique feature among small mammals native to North America ⁽⁵⁾.

During its foraging expeditions, the dark kangaroo mouse is vulnerable to a number of potential predators, including owls, foxes and badgers ⁽¹⁾.

The underground burrow systems excavated by the dark kangaroo mouse are relatively simple and unbranched ⁽⁶⁾, reaching lengths of up to 1.8 metres ⁽³⁾, and rarely being more than 30 centimetres deep ^{(3) (6)}. The entrance to the burrow is usually located near or under a shrub ^{(3) (5)}, and it is plugged by the dark kangaroo mouse when it returns after a night of foraging, to prevent water evaporation ⁽³⁾.

Between November and March, the dark kangaroo mouse retires to its burrow to hibernate during the harsh, cold winter ^{(5) (8)}. After emerging from hibernation in the spring, the breeding season takes place ⁽⁸⁾. Each litter produced by the female dark kangaroo mouse contains between two and seven young ^{(1) (4) (5) (8)}, with the majority of litters being born in May and June ⁽¹⁾. It is thought that more than one litter is produced per season ^{(1) (5) (8)}.

The male dark kangaroo mouse aggressively defends its territory, which can be up to 6,600 square metres in size, against others of its kind. Female dark kangaroo mice also establish territories, but these are generally much smaller than those of the male, with an average size of just 400 square metres ⁽⁴⁾.

Dark kangaroo mouse range

The dark kangaroo mouse is endemic to the western United States ^{(1) (11)}. Its distribution covers south-eastern Oregon, west-central Utah ^{(1) (9)}, north-eastern and central-eastern California, Nevada, and the tip of south-western Idaho ⁽¹⁾.

The dark kangaroo mouse generally occurs at elevations between 1,200 and 2,050 metres ⁽⁸⁾, higher than its less widely distributed relative, the pale kangaroo mouse (Microdipodops pallidus) ⁽¹⁰⁾.

Dark kangaroo mouse habitat

The dark kangaroo mouse occurs in dry habitats ⁽¹⁰⁾, including deserts with loose, fine sand and gravel, and sand dunes ^{(1) (8)}. The arid environments inhabited by the dark kangaroo mouse are often bordered by dried-out alkaline lakes ^{(1) (6) (10)}.

Sagebrush scrub (Artemisia tridentata) is typically present in the dark kangaroo mouse’s habitat ^{(1) (3) (6) (9)}, although other plants such as shadscale (Atriplex confertifolia) are also common ^{(1) (9)}.

Dark kangaroo mouse status

The dark kangaroo mouse is classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾.

Dark kangaroo mouse threats

Although the dark kangaroo mouse is not currently thought to be at risk of extinction, it is known to be suffering a population decrease ⁽¹⁾.

Extreme habitat alteration for the purpose of cultivation, along with the introduction of weedy grasses, has caused a decline in some populations of the dark kangaroo mouse. As well as these human-induced habitat changes, it appears that natural shifts in vegetation types have resulted in the dark kangaroo mouse being displaced by other rodent species ^{(1) (10)}. These effects may be amplified by the fact that the dark kangaroo mouse already has a rather fragmented distribution ⁽¹⁾, with the patchy and isolated distribution of the two most threatened subspecies leaving them particularly vulnerable to habitat alteration ⁽¹⁰⁾.

Dark kangaroo mouse conservation

The dark kangaroo mouse is not currently considered to be at risk of extinction, and is not known to occur in any protected areas ^{(1) (10)}.

However, 2 of the 13 subspecies of dark kangaroo mouse are thought to be of conservation concern. Despite this, neither of these subspecies has been afforded protected status ⁽¹⁰⁾.

Proposed conservation action for the dark kangaroo mouse includes the initiation of a survey and monitoring programme to investigate which human-induced or natural alterations are affecting the distribution of this species. Further surveys to determine the status of the dark kangaroo mouse’s population and its distribution limits have also been recommended ⁽¹⁰⁾.

Find out more

More information on the conservation of the dark kangaroo mouse and other North American rodents:

• Hafner, D.J. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland, and Cambridge, UK. Available at:
  http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf

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Glossary

Alkaline

Having a pH greater than 7.0. Soil is regarded as alkaline if it has a pH between 8.0 and 10.0.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Hibernation

A winter survival strategy in which an animal’s metabolic rate slows down and a state of deep sleep is attained. While hibernating, animals survive on stored reserves of fat that they have accumulated in summer.

Larva

Immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.

Nocturnal

Active at night.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Territory

An area occupied and defended by an animal, a pair of animals or a group.

References

1. IUCN Red List (July, 2012)
   http://www.iucnredlist.org/
2. Jameson, E.W. and Peeters, H.J. (2004) Mammals of California. University of California Press, California.
3. Ingles, L.G. (1947) Mammals of California. Stanford University Press, California.
4. Burnie, D. (Ed.) (2001) Animal. Dorling Kindersley, London.
5. Rafferty, J.P. (2011) Rats, Bats and Xenarthrans. The Rosen Publishing Group, New York.
6. Roots, C. (2006) Hibernation. Greenwood Publishing Group, Connecticut.
7. Bowers, N., Bowers, R. and Kaufman, K. (2007) Kaufman Field Guide to Mammals of North America. Houghton Mifflin Harcourt, Boston.
8. Reid, F. (2006) A Field Guide to Mammals of North America, North of Mexico. Houghton Mifflin Harcourt, Boston.
9. Verts, B.J. and Carraway, L.N. (1998) Land Mammals of Oregon. University of California Press, California.
10. Hafner, D.J. (1998) North American Rodents: Status Survey and Conservation Action Plan. IUCN/SSC Rodent Specialist Group, IUCN, Gland, Switzerland, and Cambridge, UK. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/1998-039.pdf
11. MobileReference (2008) The Illustrated Encyclopedia of North American Mammals: A Comprehensive Guide to Mammals of North America. MobileReference, Boston.